Recently, along with miniaturization of patterns in a semiconductor manufacturing process, there has been an increase in the number of processes in which an etching amount needs to be precisely controlled while a silicon oxide (SiO2) film is selectively etched.
For example, in a process of manufacturing a NAND flash memory device, an oxide film grown in a device isolation region is etched before an oxide-nitride-oxide (ONO) insulation film and a control gate pattern are formed above a floating gate.
In this case, when an etching amount of the oxide film is not precisely controlled, an exposure degree of a pattern of the floating gate is changed for each device region and, thus, characteristics of devices are not uniform and, when the oxide film is not selectively removed, there is a problem in that an exposed portion of a floating gate electrode is also etched during etching.
To overcome this problem, conventionally, a wet etching method or a plasma etching method is used, but the wet etching method has a difficulty in controlling an etching amount while having a high etch selectivity and is not appropriate to embody a fine pattern due to isotropic etching characteristics, and the plasma etching method is capable of embodying a fine pattern, has a difficulty in selectively removing a thin film due to a low etch selectivity, and has a problem in that charging damage occurs at a lower film due to charged particles.
Accordingly, recently, gas phase etching (GPE) of vaporizing an etchant, etc. that are used in conventional wet etching, injecting the etchant, etc. into a reactor and, then, removing a thin film via chemical reaction has been introduced and applied.
In this case, along with ammonia (NH3) for selectively etching a silicon oxide film, hydrogen fluoride (HF) gas for adjusting etching characteristics has been mainly used.
An apparatus, etc. that separately include a low-temperature chemical processing chamber in which etching is performed via gas phase etching (GPE) among the above the methods and a high-temperature thermal processing chamber that heats, vaporizes, and removes a non-volatile reaction product generated during the etching have been developed. However, there is a problem in that the size of such an apparatus becomes larger due to an increase in the number of processing chambers, a wafer needs to be transferred between the chambers, and a processing time is delayed due to a transferring time.
Accordingly, in accordance with recent trends, there has been a desperate need to develop dry etching for selectively etching a silicon oxide film and realizing control with a uniform etching amount, which is really required along with miniaturization of patterns.